rw200
Member
Good evening, all. Recently I scored some used AXR pistons and rods for my AHU build. Threw them in the (decked) AHU block using old bearings and rings to get protrusion measurements. Lots of variability across the top surface of each piston, even after I took the piston rocking into account. Eventually laid a machinists straightedge across the piston top (crosswise to the axis of the wristpin) and found that the very center was lower by 6 mils or so. The metal is not eroded, original machining marks are still there, the laser engraving was still intact until I rubbed most of it off cleaning the carbon off. Other wise the pistons looked great, no grooves, rings not gummed up, skirt coating still mostly there. All of the pistons looked like this and had the depressed center. For comparison, an old AHU piston that looked more beat up was perfectly flat across the top. And for the block, there was no trend in protrusion from one end of the block to the other so the deck was probably machined true.
So, I'll ignore the center of the AXR pistons and just use the measurements at edge of piston along wristpin. The slight dish in the piston might represent a little lost compression though.
I wonder if the oil passages in the PD (AXR) piston crown might weaken it enough to the point it deforms a little. Any thoughts?
So, I'll ignore the center of the AXR pistons and just use the measurements at edge of piston along wristpin. The slight dish in the piston might represent a little lost compression though.
I wonder if the oil passages in the PD (AXR) piston crown might weaken it enough to the point it deforms a little. Any thoughts?